Ultrasonic treatment enhances the formation of oxygen vacancies and trivalent manganese on α-MnO2 surfaces: Mechanism and application.

Catalytic activity is the main obstacle limiting the application of peroxymonosulfate (PMS) activation on transition metal oxide catalysts in organic pollutant removal. Herein, ultrasonic treatment was applied to α-MnO2 to fabricate a new u-α-MnO2 catalyst for PMS activation. Dimethyl phthalate (DMP, 10 mg/L) was almost completely degraded within 90 min, and the pseudofirst-order rate constant for DMP degradation in the u-α-MnO2/PMS system was ∼7 times that in the initial α-MnO2/PMS system. The ultrasonic treatment altered the crystalline and pore structures of α-MnO2 and produced defects on the u-α-MnO2 catalyst. According to the XPS, TG, and EPR results, higher contents of trivalent Mn and oxygen vacancies (OVs) were produced on the catalyst surfaces. The OVs induced the decomposition of PMS to produce 1O2, which was identified as the main reactive oxygen species (ROS) responsible for DMP degradation. The u-α-MnO2 catalyst presented great reusability, especially by ultrasonic regeneration of OVs toward the used catalyst. This study provides new insights into regulating OVs generation and strengthening catalyst activity in the PMS activation process for its application in water purification.

Stable isotopes reveal the formation diversity of humic substances derived from different cotton straw-based materials.

Humic substances (HS) are essential in environment processes and carbon (C) sequestration in soils. In this study, organic materials such as cotton straw and its derived compost and biochar were added to the soil on a C-equivalent basis and incubated for 30 and 180 days in order to investigate the different forms of plant biomass derived C sequestration in HS. The C distribution in humic acid (HA), fulvic acid (FA), and humin (Hu) derived from organic materials was investigated using the 13C isotope method, while the catalase, sucrose, and ß-glucosidase activities were also determined. The results showed that C3 distribution of Hu derived from straw, compost and biochar increased from 40.94% to 67.12%, 74.47% and 80.75%, respectively. In addition, the increase of C3 distribution of HA or FA derived from straw, compost and biochar were 4.69%, 10.09% and 1.49%, respectively. There were significantly positive correlations between catalase, sucrase and ß-glucosidase activities and C3 derived HA and FA. The principal component analysis showed that catalase, sucrase and ß-glucosidase were explained mainly by the first principal component indicating a significant correlation. These findings suggest that straw, compost and biochar are mainly sequestrated in Hu. Comparatively, the straw and compost are more likely to contribute to the formation of HA and FA in soil, but biochar favors the Hu, which helps in soil C sequestration. The formation of HA and FA derived from organic materials was supported by catalase, sucrase and ß-glucosidase activities.

Effect of cotton straw-derived materials on native soil organic carbon.

Different types of crop straw and their derived biochars and compost treatments have huge potential for carbon sequestration to sustain crop productivity. In this study, cotton straw (straw), cotton straw-derived compost (compost) and cotton straw-derived biochar (biochar) with equivalent carbon (C) content were added to soil and incubated for 30 and 180 days. The C sequestration potential of these organic materials was determined by 13C isotope trace method. The structural characteristic of soil organic carbon (SOC) was analyzed by solid-state 13C NMR spectroscopy. The SOC concentration was measured by wet oxidation and dry combustion methods. The results showed that 50.84%, 41.03% and 38.55% of native SOC were replaced by biochar, compost, and straw, respectively. The carbohydrate C and methoxyl C contents were significantly higher in straw and biochar amendments respectively, while phenolic C and alkyl C were high in compost amendment and a higher proportion of aryl C occurred in biochar treatment. These findings revealed that straw material was easier to be decomposed, but compost and biochar showing better stability.

[Isolation and identification of dominant microorganisms in rhizosphere of continuous cropping with peanut].

OBJECTIVE: We isolated and identified dominant microorganisms from the rhizosphere of continuous cropping with peanut, to study the relationship between dominant microorganisms and peanut continuous cropping. METHODS: By using dilution-plate method we isolated dominant bacteria, dominant fungi and actinomycetes from the rhizosphere of continuous cropping with peanut. Morphological specificity, culture shape, physiological-biochemical characteristic and partial 16S rDNA sequences were used to identify bacteria and actinomycetes. Morpholog, growth on various media, and Internal Transcribed Spacer (ITS) rDNA sequences homology analysis were performed to identify dominant fungi. RESULTS: We isolated seven dominant bacteria strains, seven dominant fungi and seven dominant actinomycetes. Dominant bacteria were identified as Leifsonia xyli, Arthrobacter chlorophenolicus, Microbacterium flavescens, Sphingomonas sp., Pasteurella sp., Bacillus simplex and Bacillus megaterium. Dominant fungi were identified as Cladosporium cladosporioides, Penicillium purpurogenum , Hypocrea lixii, Exophiala pisciphila, Penicillium janthinellum, Aspergillus sp. and Verticillium dahliae. Dominant actinomycetes were identified as Streptomyces violaceoruber, Streptomyces flaveus, Streptomyces panaciterrae, Streptomyces achromogenes, Streptomyces pseudogriseolus, Streptomyces cellulosae and Streptomyces aureus. CONCLUSION: This study was the first time to isolate and identify dominant microorganisms from the rhizosphere of continuous cropping with peanut. The type of dominant microorganisms changed obviously after planting peanut, although the change was without regularity.